Escape-limited maximum energy at perpendicular shocks in the interstellar magnetic field

Abstract

We investigate the maximum energy limited by the escape from a perpendicular shock region of a spherical shock in the interstellar medium (ISM), and the size of the rapid acceleration region. The perpendicular shock of supernova remnants (SNRs) has been expected to be PeVatrons without a magnetic field amplification in the upstream region. We perform test particle simulations, showing that the escape-limited maximum energy in the perpendicular shock is about a few 10 TeV for the typical type Ia SNRs. In addition, we show that, in the free expansion phase, the rapid perpendicular shock acceleration realizes in about 20% area of the whole shock surface, which is much larger than the superluminal shock region.